The four Spain internationals were also joined by Argentine duo Lionel Messi and Javier Mascherano, who did warm-up drills and jogged in Thursday's training sessions but participated in their first full session with the group on Friday.

The club continues to be buoyed by the progress of Messi, who was held out of last week's friendlies with the Argentine national team against Paraguay and Ecuador due to a swollen foot that was so painful that he couldn't even put on a pair of boots in the beginning of the tour of the United States.

Messi's completion of Friday's training, without incident, is encouraging for his chances of starting in Sunday evening's match in Balaidos.

However, Luis Enrique will be without Jordi Alba, who was forced to leave the Spanish national team camp early after suffering an injury in their win over Ukraine, and Thomas Vermealen continues to split his time between individual and group drills as the commanding Belgian continues to work his way back from muscle surgery and toward his Barcelona debut.

Thomas Conn

I didn't particularly enjoy football growing up, but I respected it. However, after living in Barcelona for over a year, my future wife took my to watch a meaningless Champions League draw between Barcelona and FC Basel on a rainy night in November. Messi would score that evening and I would fall madly under the spell of Spanish football. I have loved this sport and every single detail ever since that day (Barcelona went on to beat Manchester United in the final in Rome that year). Tom has finely tuned his craft as the owner of Inside Spanish Football for the past four years.